1. Field of the Invention
The present invention generally relates to apparatuses used for floor finishing, particularly floor grinding and polishing, and more particularly to concrete floor grinding and polishing machines.
2. Description of the Related Art
Polished concrete has made tremendous growth over the past decade and is a result of taking what is a traditional building product (i.e., concrete flooring) and making it an attractive floor finish. It provides a wide spectrum of varying color choices and surface finishes. Grinding and polishing concrete (also referred to herein as polishing concrete) is a true mechanical process which does not require a film-forming membrane and should not be confused with sealed concrete.
Typically the concrete goes through a process of grinding and polishing using aggressive equipment and abrasive elements or tooling, including abrasive pads of varying grits from 30 to 3,000. The pads are drivably supported on a plurality of rotatable spindle pads driven by a machine-mounted electric motor. The process may utilize a concrete hardener that enables the concrete to chemically alter itself into a much more dense and liquid-resistant surface, and may yield a mirror finish on the surface of the concrete slab.
Oftentimes existing concrete floors with years of old and otherwise failing floor covering can be turned into an attractive functional floor having a total life, with proper maintenance, that will outlast other flooring options. Polished concrete floors are very easy to maintain, and typically require much less and less expensive care than other types of flooring surfaces.
If the unpolished concrete has some type of topical coating or adhesive present, it is first removed using a prep style abrasive before the process of grinding and polishing the floor may begin.
The grinding and polishing process begins by equipping a grinding and polishing machine with grinding pads or tools that have grits of 30, 70, and 120, which are used successively. These abrasive elements are preferably diamond pads, such as, for example, BevelKut™ diamond discs available from Kut-Rite Manufacturing; they are used successively in those three grits. These abrasive elements are rotated at a relatively slow speed during the grinding steps, e.g., at rotating speeds in the range of about 500 to 800 rpm.
After completion of grinding the floor with the diamond pads, honing steps follow using grinding or polishing pads or tools that have grits of 50, 100, and 200, rotated at, for example, a speed of about 800 rpm. These abrasive elements are preferably resin pads, and are also available from Kut-Rite Manufacturing. After the 200 grit resin pad honing step, dies or stains may be applied to the concrete to provide the desired flooring color. If necessary, a concrete densifier is then applied to the floor.
The grinding and polishing process then continues with polishing steps using a 400 grit resin pad applied to the floor at a relatively higher speed. During the polishing steps, the rotational speeds of the spindles and abrasive elements may be in the range of about 800 to 1,100 rpm. During the polishing step(s), the concrete will start to develop a sheen that will vary with clarity depending on which resin pad grit you are polishing with. For example, the polishing subprocess may be continued through a succession of steps including polishing with resin pads of a type available from Kut-Rite Manufacturing having grits of 800, 1,500 and 3,000, the higher grit numbers generally corresponding to higher spindle rotational speeds. The grit choice of the final resin pad used in the polishing subprocess will depend on the reflection and shine desired of the resulting polished concrete floor. If the polishing process is continued through use of a 3,000 grit polishing pad, for example, the concrete should have a mirror-like finish that almost resembles the look of glass. A burnishing pad may be optionally used at the highest polishing speed after all polishing steps are complete to finish the cleaning process of the concrete floor and give it its ultimate shine. If desired, a topical sealer may be optionally applied to the finished concrete floor.
The concrete floor grinding and polishing process may be dry or wet. It is known to provide a water tank on-board the grinding and polishing machine from which a source of water is provided to the concrete floor. The diamond pads and resin pads may be provided with channels through which the water may be channeled.
The machine may also be provided with a vacuum inlet disposed near the tool pads. Typically, the tool pads are enclosed by a shroud that is in proximity to the floor and surrounds the rotating pads. The vacuum port is connected by a hose to an externally-provided vacuum, which may be nearby or wheeled alongside the grinding and polishing machine.
An example of a prior concrete floor grinding and polishing machine includes a magnetic quick-disconnect tool mounting design by which the diamond and resin tools are mounted to the bottom of the machine. The quick-disconnect system incorporates two locating pins that precisely position each of these abrasive elements on its respective spindle pad, which uses powerful neodymium rare earth screw magnets to hold the tools in place thereon. This arrangement provides a tool system that facilitates quick and precise placing of the tools on the spindle pads for smooth running and holding power that prevents the tools from becoming disengaged with the spindle during operation and facilitates fast removal and replacement of the pads. A known tool pad change procedure includes the following steps: with the motor off, lifting the front end of the machine to distance the tool from the floor, and holding it in a lifted position to gain access to the spindles and the tool pads that are connected thereto; locating a disconnect tab on the magnetic tool holder plate affixed to each spindle; using a screw driver, disconnecting a metal hook from the disconnect tab, and disconnecting a loop puck attachment or metal bond plate from each magnetic tool plate and removing the tool; and positioning a replacement tool (e.g., a diamond or resin pad of the next grit to be used) on each tool plate by lining up two holding pins in the tool plate with corresponding holes in the tool, and reconnecting the loop puck attachment or metal bond plate to the magnetic tool plate, and reconnecting the metal hook to the disconnect tab.
According to one prior machine, a serpentine belt drive is provided by which the single electric motor is in driving engagement with three spindles which rotate about their respective axes in a common direction (i.e., either clockwise or counterclockwise). The serpentine belt may provide up to about 70% contact with the circumference of the pulley driven by the electric motor, and more than 50% contact with the circumference of each of the spindle pulleys rotatably fixed to their respective spindles. Typically the electric motor is of a heavy, cast iron casing type that provides a substantial amount of downward force on the floor, the machine typically weighing as much as 350 to 400 lbs.
The motor may be a single or three-phase electric motor typically having a power rating between five and seven and one half horsepower. The motor is preferably reversible, and it is desirable to periodically operate the motor, and thus rotate the grinding or polishing pads attached to the spindle pads, in opposite directions to open up their abrasive surfaces, dislodging debris that may be captured within their abrading surfaces. This prevents them from becoming clogged or glazed, and thereby extends their life. The motor may also be of variable speed, with slower speeds preferred for grinding operations and higher speeds preferred for polishing operations. The rotating motion of the spindles is performed at a slower speed to perform the earlier steps of the process associated with grinding and honing the concrete floor, whereas the planetary motion of preferably faster-rotating spindles about a central axis, e.g., the motor axis, provides a desirable consistency during the steps associated with polishing.
An example of a prior concrete floor grinding and polishing machine includes a plurality of spindles, with each spindle rotatable at a first speed about its respective axis of rotation. Typically, the spindle positions are held fixed relative to the machine during grinding operations. The spindles may, however, be rotatably attached to and part of a bowl assembly that is itself rotatable about a central axis coincident with the motor axis. The spindles are distributed about a central axis, and also revolve thereabout as satellites, to provide a consistent polishing pattern that is not unlike that which may be created by the Spirograph drawing toy famously marketed in the United States by Hasbro, Inc. and/or Kenner, Inc. The planetary motion of the spindles at a second speed about the bowl central axis may be driven by the electric motor, or it may be passive, with the planetary motion being indirectly driven by the frictional engagement between the rotating abrasive tools and the floor.
A control panel on typical grinding and polishing machines includes an emergency stop button, an on/start button, and a potentiometer by which the rotation speed of the spindles may be changed. Additional controls may include an alarm light, a tachometer, an alarm reset button, and a reverse/forward switch by which the motor direction may be changed. The machine may include an electronic controller box carrying all necessary power conversion circuits for operating the motor. Thus, it is known to utilize a single machine for both grinding and polishing steps, with each of the grinding steps done at a relatively slower speed with the spindle axes held fixed relative to the machine, and each of the polishing steps done at a relatively higher speed with the spindle axes having planetary motion about the single motor axis. The grinding and polishing steps are therefore necessarily performed sequentially, with each step respectively requiring the operator's time.
Although some prior machines are quite effective, it is generally desirable to reduce the time, and thus the labor cost, involved in the grinding and polishing process, and to have capabilities in a single machine that accommodate process variations which can save time and provide process flexibility, and eases its transportation, maintenance, and the abrasive tool replacement that typically occurs multiple times during the grinding and polishing process.